Matthew Shupe Von Walden David TurnerU. Colorado/NOAA-ESRL U. Idaho NOAA - NSSL

New Cloud Observations at Summit, Greenland:

Expanding the IASOA Network

Special thanks to the ICECAPS team, including: Ralf Bennartz, Maria Cadeddu, Ben Castellani, Chris Cox, David Hudak, Mark Kulie, Nate Miller, Ryan Neely, William Neff, and many others

Why Are Clouds Important… Particularly in the Arctic?

• Relatively few observations = less understanding relative to low latitudes

• Mixed-phase processes occur frequently• Complex interactions/feedbacks with

seasonally high-reflective surface• Atmosphere is cold and dry (increasing

cloud radiative importance)• Little is known about Arctic aerosol

populations and sources• Large-scale Arctic meteorology is poorly

constrained in models/reanalyses

IASOA: International Arctic Systems for Observing the Atmospherewww.iasoa.org

Detailed Cloud Observatories Newest Cloud Observatory: Summit, est. 2010

SHEBA

Anatomy of a Cloud Observatory

RadiosondesT, q, winds, phase

Cloud radarBoundaries, micro, phase, dynamics

Lidar or ceilometerCld base, phase,

micro

Microwave radiometerLWP, PWV

AERIEmissivity, phase, size

Broadband RadiometersLW, SW

These instruments together can be used to characterize cloud macrophysical, microphysical, radiative, and dynamical properties.

Why is it important to observe/study clouds over the Greenland Ice Sheet?

Source: Precipitation => The Mass Budget

Sink: Radiation => The Energy Budget

What have we learned from the first 1.5 years of cloud observations at Summit?

Total Cloud Occurrence

• “Cloud” is defined as hydrometeors in the atmosphere that are detected by the remote sensor suite.

• Summit is very cloudy, more than Arctic average.• NyAlesund and Atqasuk are likely underestimated

Cloud Occurrence with Height

• Instrument outages at Summit result in limited statistics in some months• Summit has frequent low-level fogs and layers of ice crystals

Occurrence of Cloud Liquid Water

• Similar annual cycle trend at all sites: summer/fall maximum.• Despite cold temperatures, and long distances to moisture sources, cloud

liquid water occurs 25% of the time at Summit (Similar to Eureka, Canada)

• LWP derived from microwave radiometer brightness temperatures• Most Arctic clouds are thin ( LWP < 50 g/m2)• “Thick” clouds are virtually non-existent at Summit

Low-cloud Liquid Water Amount

• Remarkable similarity between Summit and other observatories, despite dramatic difference in elevation!

Low-cloud Boundaries

q qE

High backscatter + low depol = liquid

Mixed-Phase Cloud Structure

High reflectivity + high depol = ice precip

Velocity variability

Cloud mixed-layer

Cloud microphysical-dynamical relations are similar!

W-LWP-IWP correlation

Cloud-generated turbulence

Cloud ice nucleates in liquid

Thermodynamic profiles and clouds

•Surface-based T and q inversions at ~ 100-300m, almost always present•Clouds occur when there is relatively moist & warm advection aloft

(~15 C warmer, 4x moister)

Final Thoughts• New cloud observatory at Summit provides the

first detailed view of cloud processes over the GIS

• Initial Results:• Summit is very cloudy• Less liquid water than most other

observatories, but still 10-50% by month.• Similar low-cloud properties and processes

• Striking similarities suggest that cloud processes might be relatively consistent across the Arctic (while the meteorological context varies).

• Future directions:• Impact of clouds on surface energy budget• Better understanding of precipitation budget

Collaborations welcome and encouraged!